1. Field of the Invention
The present invention relates to wheelchairs. In particular, the present invention relates to wheelchairs having reclinable seat backs.
2. Description of the Related Art
As is well known in the art, the comfort of a person using a wheelchair often can be enhanced by adjusting the angle of the wheelchair's seat back. Consequently, many arrangements have been proposed and employed to provide a wheelchair with a reclining seat back.
In a typical construction, the seat back panel is supported by a pair of side posts pivotally connected to the wheelchair chassis proximate the rear edge of the seat bottom. A telescoping strut is connected between the upper end of each side post and a point on the chassis. The struts elongate as the seat back is moved toward an upright position and contract as the seat back is reclined.
In one seat back arrangement presently in use, each strut comprises a tubular lower member pivotally connected to the chassis below and behind the seat bottom and a rod-shaped upper member pivotally connected to one of the side posts and received in the lower member. The handles for the wheelchair are fixed to the upper ends of the upper strut members, which are rotatable about the strut axes. The outer surface of the upper strut member received in the lower strut member has a longitudinally extending flat formed therein and includes threads formed over the remainder of its circumference. These threads mesh with a threaded engagement member brazed on the lower strut member to lock the seat back in a desired angular position relative to the seat bottom. When the wheelchair attendant rotates the handles outwardly, the threads of the upper members disengage from the engagement members of the lower members, and the attendant can elongate or contract the struts to adjust the inclination of the seat back.
Although the above-described reclining wheelchair design has met with commercial success, it can be unwieldy when the attendant attempts to adjust the position of the seat back while the wheelchair is occupied, particularly when occupied by a heavy patient. Releasing the engagement between the upper and lower strut members requires the attendant to support the weight of the patient during adjustment. When the attendant rotates the two handles outwardly to unlock the seat back, however, he or she typically exerts a downward force on the seat back just as it is released. Quick reflexes and considerable strength often are required to prevent the seat back from snapping to the reclined position while occupied.
The present invention is intended to provide a wheelchair with a reclining seat back that can be adjusted easily while the wheelchair is occupied.
The present invention also is intended to provide a reclining seat back with a release mechanism actuated in a manner that will naturally resist sudden downward movement of the seat back.
Additional advantages of the present invention will be set forth in part in the description that follows, and in part will be obvious from that description or can be learned by practice of the invention. The advantages of the invention can be realized and obtained by the apparatus particularly pointed out in the appended claims.